The present invention relates to an electronic compressed air system for vehicles.
WO 98/47751 A1 describes a pneumatic vehicle brake system provided with a compressor, at least one air-load circuit, such as service-brake circuits, a parking-brake circuit, a low-pressure auxiliary circuit and a high-pressure circuit, wherein the circuits are provided with compressed air reservoirs and demand valves. Between the compressor and the at least one load circuit, there are disposed first electrically actuatable valves, which are closed in the de-energized normal state, and, between the compressor and the auxiliary circuit, there is disposed a second electrically actuatable valve, which is open in the de-energized normal state. The valves are actuated by an electronic control unit. The outlet ports of the first valves of the air-load circuits are in communication via check valves with the outlet port of the second valve, which is open in the de-energized normal state. If a compressed air demand exists in one of the load circuits, for example due to too-low reservoir pressure, the corresponding valve is activated by the control unit, whereby the air demand is covered by the compressor, while at the same time the second valve for the auxiliary circuit is closed. Failure of the compressor leads to a pressure drop, which is detected by the control unit, which closes the valves or keeps them closed, whereby the pressure in the circuits is maintained. A pressure-regulating valve determines the pressure level. In the event of failure of the pressure-regulating valve, overpressure is relieved via an overpressure valve. Pressure sensors monitor the circuits. The circuits are supplied with air via the second, normally open valve and via the check valves connected upstream from the circuits. If the electrical system fails, all valves go to normal state. Nevertheless, the compressor continues to run and supplies the circuits with air via the second, normally open valve of the auxiliary circuit, the system pressure being determined by a low-pressure relief valve of the auxiliary circuit. If one valve fails, the associated circuit can be supplied with air via the valve of the auxiliary circuit and the check valve. The known system is complex, since each load circuit is equipped with a compressed air reservoir.
DE 10004091 C2 describes a compressed air supply device for vehicle compressed air systems with a multi-circuit protective valve, a pressure regulator, a supply line for supplying the circuits of the multi-circuit protective valve with compressed air, and a compressor, which can be switched by means of a pneumatic switching device, a pilot valve for controlling the pressure regulator and the switching device being provided, and a throttle being interposed between the pilot valve and the switching device. Each circuit is provided with a compressed air reservoir. The pilot valve is controlled and/or regulated by an electronic control and/or regulation unit. Pressure sensors monitor the pressure in the circuits and in the supply line.
In vehicles with a compressed air brake system, it is known that the EU Brake Directive can be satisfied by providing separate compressed air reservoirs for the front-axle and rear-axle brake circuits. Additional compressed air reservoirs are used for other compressed air consumers, such as an air-suspension circuit, to ensure that the functionality of the brake system is not negatively influenced by the operation of such further compressed air consumers. Such known compressed air systems with separate compressed air reservoirs for a plurality of compressed air load circuits are quite costly.